Previously, many types and styles of power driven wrenches have been used in endeavoring to provide an effective means to drive a nut along an extended shaft. Some tools utilize open ended radial slots admitting the workpiece with a hexagonal socket to register with the nut. Others use splined gears to attach separate adapter tools for breakaway capabilities. Others use conventional drill motors to provide the electromotive force.
A search of the prior art did not disclose any patents that read directly on the claims of the instant invention, however, the following U.S. patents were considered related:
______________________________________ Patent No. Inventor Issue Date ______________________________________ 4,322,989 Garolis Apr. 6, 1982 4,240,310 Roth Dec. 23, 1980 4,171,651 Dacunto Oct. 23, 1979 3,987,692 Lesner et al Oct. 26, 1976 3,791,242 Bartusch Feb. 12, 1974 3,257,877 Ulrich et al Jun. 28, 1966 ______________________________________
Garolis discloses an electric motor, with a removable case, driving a shaft with a worm gear driving a ring gear. A coupling on the shaft allows the motor to be removed. The work engaging gear ring fits the work without the use of a compensating socket, however, the ring must be changed to the desired configuration.
Roth utilizes a socket wrench that has a holder containing a socket rotatably driven from a separate rotary power tool, such as an electric drill. The configuration is such that the device is thin enough to fit into closely confined spaces.
Dacunto teaches a power driven socket wrench that swivels about the axis of the output shaft. A single clamping screw locks the assembly in place, and the rotating socket contains an arcuate slot in the wrench housing for engaging the workpiece.
Lesner et al, on the other hand, employ an air motor for rotational force and use a similar slotted end socket member. The motor is reversible and a cluster of gears provide the speed reduction. One of the objects of this invention is to improve the method of re-registering the slots, which is accomplished by a combination of the reversing feature of the motor and detent means.
Bartusch is directed to an electric motor powered wrench with a connecting rod using a worm gear eccentric crankshaft mechanism. The connecting rod imparts successive rotational movements to a ratchet gear rotating the socket or an adapter for impacting actuation of the mechanism for breaking loose objects to be rotated.
Ulrich et al also use an air motor having a constant speed ratio initially, with automatic shifting into a different drive ratio during final stages of operation. This change in ratio is sensed by a preset torque valve changing the relationship of a planetary gear train.
It will be noted, however, that the combination of variable speed and reversible mode of operation has not been found in any of the prior art thus discovered.